CN112328626B - Searchable encryption method facing cloud environment and supporting fuzzy keyword sequencing - Google Patents
Searchable encryption method facing cloud environment and supporting fuzzy keyword sequencing Download PDFInfo
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Abstract
The searchable encryption method for supporting fuzzy keyword sequencing for the cloud environment has higher efficiency and more practical significance. The invention comprises the following steps: the system is established and initialized to generate public parameters, a master key and a secret key; the data owner extracts a keyword set according to the plaintext document set, generates a reverse index table and a fuzzy index table and sends the reverse index table and the fuzzy index table to the cloud server; the data owner encrypts the plaintext document set by using the master key to generate a ciphertext document set and sends the ciphertext document set to the cloud server; constructing a trap door by a data user, encrypting the trap door and sending the encrypted trap door to a cloud server; after the cloud server receives the encrypted trapdoors, the trapdoors are obtained through decryption by using a private key, and the required documents are ordered according to the relevancy and sent to a data user; the data user sends the attribute set of the data user to the trusted authority, and if the attribute set can pass the access control structure, the trusted authority sends the decryption key to the data user; and the data user decrypts the ciphertext document set to obtain the required plaintext document.
Description
Technical Field
The invention relates to a searchable encryption method supporting fuzzy keyword sequencing and oriented to a cloud environment.
Background
With the development of big data and cloud computing, more and more users and enterprises choose to store data on a cloud server in an encrypted manner. To retrieve data of interest to them, the key technology of searchable encryption may be employed. Sometimes, the data owner wishes to share encrypted data to certain users without revealing privacy.
In the prior art, searchable encryption schemes are generally divided into symmetric searchable encryption and asymmetric searchable encryption. The efficiency of the symmetric searchable encryption is higher than that of the asymmetric searchable encryption, but the asymmetric searchable encryption is suitable for a scene shared by multiple persons and more practical, because the symmetric searchable encryption requires a data user to share an own encryption key with a multi-bit data user, the security of the key is greatly reduced, and the efficiency of a scheme is greatly reduced by only introducing a public key cryptosystem in the searchable encryption. Therefore, how to design a searchable encryption scheme with higher efficiency and more practical significance has become a focus of attention in the field of cryptography.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides a searchable encryption method facing the cloud environment and supporting fuzzy keyword sequencing, designs a new fuzzy keyword searchable attribute-based encryption scheme supporting sequencing, and has higher efficiency and more practical significance.
The technical scheme adopted by the invention for solving the problems is as follows:
a searchable encryption method facing cloud environment and supporting fuzzy keyword sequencing is characterized in that: the method comprises the following steps:
firstly, establishing and initializing a system, and generating a public parameter PP, a master key MK and a key K;
step two, generating an index: the data owner sets D ═ D according to the plaintext document set 1 ，D 2 ，...，D n Extracting a keyword set W ═ W } ═ W 1 ，W 2 ，...，W m Generating a reverse index table and a fuzzy index table, and sending the reverse index table and the fuzzy index table to the cloud server;
step three, an encryption stage: the data owner encrypts the plaintext document set D by using the master key to generate a ciphertext document set CT, and sends the ciphertext document set CT to the cloud server;
step four, a trapdoor generation stage: constructing a trapdoor by a data user, encrypting the trapdoor and sending the trapdoor to a cloud server;
step five, retrieval stage: after the cloud server receives the encrypted trapdoors, the trapdoors are obtained through decryption by using a private key of the cloud server, and the required documents are ordered according to the relevancy and sent to the data user;
step six, key obtaining stage: the data user sends the attribute set of the data user to the trusted authority, and if the attribute set of the data user can pass through the access control structure, the trusted authority sends the decryption key to the data user; otherwise returning to T;
step seven, a decryption stage: and the data user decrypts the returned ciphertext document set to obtain the required plaintext document.
In the first step of the invention, the public parameter generation step is as follows:
(1) the data owner runs the setup function and selects an order primeBilinear group G with number p and generator G 0 Then from the minimal non-negative complete set of residuals Z of the prime number p p Selects three random numbers alpha, beta, r, and then issues common parameters
PP＝G 0 ，g，h＝g β ，e(g，g) α ；
(2) Setting the Master Key MK to (. beta., g) α ) Then, a security parameter λ is selected, and a key K ═ 0, 1 is generated λ ；
(3) The data owner specifies the access control structure tau.
The access control structure tau of the invention is a tree, and each leaf node in the tau is composed of an attribute and a threshold k x 1 is formed; a non-leaf node is a threshold gate consisting of its child nodes and a threshold; set num x Is the total number of child nodes, k, of node x in the tree x Is the threshold value, and k is set to 0. ltoreq. k x ≤num x If k is x 1, the threshold gate is an OR gate, if k x ＝num x AND the threshold gate is an AND gate.
The steps of generating the reverse index table of the invention are as follows:
(1) setting the order of the reverse index table to (n +1) × (m + 1);
(2) setting the element of the first column (i +1, 1) coordinate of the inverted index table as the encrypted document Enc K (id(D i ))，1≤i≤n；
(3) Setting the element of the first row (1, j +1) coordinate of the reverse index table as an encrypted English keyword Enc K (W j )，1≤j≤m；
(4) Document D for elements of the remaining (i +1, j +1) coordinates in the inverted index table i And a keyword W j Correlation score RF (W) of (2) j ，D i ) Filling;
(5) multiplying RF (W) by a random number r j ，D i )；
(6) An inverted index table is generated.
The method for generating the fuzzy index table comprises the following steps:
(1) setting a fuzzy index table to be of (Q +1) × (m +1) order;
(2) chinese keyword w according to Shingle method j Shingle is vector S' j ；
(3) Performing Q times of minimum hash calculation on the vector S by using Q MinHash functions to obtain Q real numbers, and forming a signature vector by using the Q real numbers;
(4) setting the element of the first row (1, j) coordinate of the fuzzy index table as an encrypted English keyword Enc K (W j )，1≤j≤m；
(5)
(6) And generating a fuzzy index table.
The document encryption method comprises the following steps:
selecting a polynomial q for each node x (including leaf nodes) in the access control structure tau x (ii) a Traversing the whole access tree from top to bottom starting from the root node R of the access control structure tau, and enabling the polynomial q x Degree d of x Threshold k of node x x Small 1, i.e. d x ＝k x -1；
Starting from the root node R, the algorithm selects a random number s ∈ Z p Let q be R (0) S, then randomly select d R Defining other points; for any other node x, let q x (0)＝q parent(x) (index (x)), and selecting the other d x Points are defined; let Y be the leaf node of τ, the document will encrypt according to the access tree line of sight, compute the ciphertext CD:
wherein, the ciphertext CT ═ C 1 ，C 2 ，...，C n ，C i ＝D i e(g，g) αs ，1≤i≤n。
The trap door is constructed as follows:
1) representing the Chinese keyword w into a banded set;
2) generating the same random vector S' according to the strip set;
3) generating a signature vector T by using the same Q min hash functions;
4) randomizing the signature vector T to obtain a vector T';
5) calculating the Euclidean norm d (T, T');
6) and generating a trap door T according to the vector T', the Euclidean norm d and the total number mun of the required documents W 。
The trap door obtaining method comprises the following steps:
1) cloud server decrypts trapdoor T with own public key w Obtaining an Euclidean norm d, a vector T' and a required document total number num;
2) the expansion vector T' is a set L;
3) converting each signature vector T stored in the fuzzy index table into a set L ', and calculating the Jaccard similarity JS between the set L and the set L'; provided JS ≠ 0, the two sets are similar, provided JS ≠ 0, calculating the euclidean norm d 'between the signature vectors T and T';
4) the error between the Euclidean norm d' and the Euclidean norm d of the keyword does not exceed a threshold value epsilon;
5) and acquiring corresponding documents according to the reverse index table, acquiring the relevance scores of the documents and the keywords in the reverse index table, and sending the documents to the data user in an ordered manner according to the rule that the relevance scores are from large to small.
The concrete process of the sixth step of the invention is as follows: the trusted authority receives the attribute set Att, and if the attribute can be accessed to the control structure, the trusted authority selects a random number a E Z p And selecting a random number a for each attribute k ∈ Att k ∈Z p 。
Calculating a secret key
Introducing a recursive algorithm DecryptNode (CD, SK, x), and if the node x is a leaf node, enabling the node x to be a branch node
i Att (x), if i ∈ Att, then
If it is used
DecryptNode(CD，SK，x)＝⊥。
When x is not a leaf node, assuming z is all the child nodes of x, DecryptNode (CD, SK, z) is computed, and the output is stored as F z Let S stand out x Is of arbitrary size K x Is such that F z And ≠ T. If no such set exists, then the function returns ≠ T. Otherwise, calculating
Let a be DecryptNode (GD, SK, x).
Trusted authority TAC sending
To the data user.
In step seven of the present invention, decryption is performed by the following formula:
CT/(e(C，R)/A)＝CT/(e(h s ，g (α+a)/β )/e(g，g) as )＝D。
compared with the prior art, the invention has the following advantages and effects:
(1) and realizing keyword search of the data owner. The data user encrypts the document with his/her own key and then uploads it to the cloud server, so he/she can search for the relevant ciphertext document and decrypt it.
(2) And realizing keyword search of data users. By introducing an attribute set encryption scheme based on a ciphertext strategy into a symmetric searchable encryption scheme, the invention can solve the problem that data cannot be shared with a plurality of users. The attribute of the data user can obtain the decryption key as long as the attribute can pass the access control policy of the trusted certificate authority.
(3) And (5) fuzzy keyword searching. The invention considers almost all typing errors, thus realizing fuzzy search, leading the user to obtain more meaningful and more accurate results, and avoiding the problem that the user can not search related documents because of typing one letter by mistake.
(4) A probabilistic trapdoor. The invention is based on probabilistic trapdoors, so that indistinguishable attacks can be resisted, and the privacy of outsourced documents and search queries can be protected.
(5) And (5) sorting the documents. The invention uses the Relevance Frequency formula to calculate the relevancy of the keywords and the documents, so that the documents can be ranked. The data consumer can thus obtain the top-k documents that are most needed.
Detailed Description
The present invention is further illustrated by the following examples, which are illustrative of the present invention and are not to be construed as being limited thereto.
In this embodiment, a searchable encryption method supporting fuzzy keyword ranking for a cloud environment includes the following steps:
firstly, establishing and initializing a system, and generating a public parameter PP, a master key MK and a key K;
and (3) generating common parameters: bilinear group G with input order p and generator G 0 And a safety parameter lambda, the output common parameter PP ═ G 0 ，g，h＝g β ，e(g，g) α The master key MK ═ β, g α ) Key K ← {0, 1} λ 。
The specific process is as follows:
(1) the data owner runs the setup function, selects a prime number p of order, and generates a bilinear group G of element G 0 Then from the minimal non-negative complete residual coefficient set Z of the prime number p p Selects three random numbers alpha, beta and r, and then issues common parameters
PP＝G 0 ，g，h＝g β ，e(g，g) α ；
(2) Setting the Master Key MK to (. beta., g) α ) Then a security parameter lambda is selected to generate a key
K＝(0，1) λ ；
(3) The data owner specifies the access control structure tau. τ is a tree, each leaf node in τ is defined by an attribute and a threshold k x 1. A non-leaf node is a threshold gate made up of its child nodes and a threshold. Set num x Is the total number of child nodes, k, of node x in the tree x Is the threshold value, set to 0 ≦ k x ≤num x If k is x 1, the threshold gate is an OR gate, if k x ＝num x AND the threshold gate is an AND gate.
Step two, constructing an index: data owner from clear text document set D ═ D 1 ，D 2 ，...，D n Extracting a keyword set W ═ W 1 ，W 2 ，...，W m And generating a reverse index table and a fuzzy index table, and sending the reverse index table and the fuzzy index table to the cloud server.
(1) The steps of generating the reverse index table are as follows:
(11) calculating the correlation degree of the keywords and the documents by using a Relevance Frequency formula, wherein if n documents and m keywords exist, the constructed reverse index table is actually a matrix of (n +1) × (m + 1);
(12) the element of the first column (i +1, 1) of the inverted index table is set as the encrypted document number Enc K (id(D i ))，1≤i≤n；
(13) Setting the element of the first row (1, j +1) of the inverted index table as the encrypted Chinese keyword Enc K (W j )，1≤j≤m；
(14) Document D for the rest elements (i +1, j +1) in the inverted index table i And a keyword W j Correlation score of RF (W) j ，D i ) Filling;
(15) masking RF (W) for improved security j ，D i ) Multiplying RF (W) by a random number r j ，D i )；
(16) The generated inverted index table is shown in the following table:
| Enc K (W 1 ) | Enc K (W 2 ) | … | Enc K (W m ) | |
| Enc K (id(D 1 )) | r×RF(W 1 ，D 1 ) | r×RF(W 2 ，D 1 ) | … | r×RF(W m ，D 1 ) |
| Enc K (id(D 2 )) | r×RF(W 1 ，D 2 ) | r×RF(W 2 ，D 2 ) | … | r×RF(W m ，D 2 ) |
| Enc K (id(D n )) | r×RF(W 1 ，D n ) | r×RF(W 2 ，D n ) | … | r×RF(W m ，D n ) |
wherein RE (W) j ，D i ) 1≤j≤m，1≤i≤n Is a document D i And a keyword W j R is a random number.
(2) The step of generating the fuzzy index table is as follows:
(21) setting a fuzzy index table to be of (Q +1) × (m +1) order;
(22) chinese keywords w according to the Shingle method j Shingle is vector S' j ；
(23) MinHash function f: s → R may map a vector S to a real number R. Performing minimum hash on the vector S for Q times by using Q MinHash functions to form a signature vector;
(24) setting the first row (1, j) of the fuzzy index table as the encrypted Chinese keyword Enc K (W j )，1≤j≤m；
(25)
Expressed is a pair of terms w j Generated random vector S' j And performing minimum hash once to obtain a real number R.
(26) The fuzzy index table generated is as follows:
thirdly, the data owner encrypts the plaintext document set D by using the master key to generate a ciphertext document set CT, and sends the ciphertext document set CT to the cloud server; the encryption process is as follows: input plaintext document D ═ D 1 ，D2，...，D n Access tree tau, output ciphertext
Wherein the ciphertext document set CT ═ C 1 ，C 2 ，...，C n ，C i ＝D i e(g，g) as ，1≤i≤n。
The method comprises the following specific steps:
the data owner de-encrypts the document according to the access control structure tau. Selecting a polynomial q for each node x (including leaf nodes) in the access control structure τ x . Traversing the whole access tree from top to bottom starting from the root node R of the access control structure tau, and enabling the degree d of the polynomial qx x Threshold k of node x x Small 1, i.e. d x ＝k x -1。
Starting from the root node R, the algorithm selects a random number s ∈ Z p Let q be R (0) S, then randomly select d R And the other points are defined. For any other node x, let q x (0)＝q parent(x) (index (x)), and selecting other d x Points are defined. Let Y be the leaf node of τ, the document will encrypt according to the access tree line of sight, compute the ciphertext CD:
wherein CT is C 1 ，C 2 ，...，C n ，C i ＝D i e(g，g) αs ，1≤i≤n。
The data owner sends the set of encrypted documents to the cloud server.
Step four, constructing a trapdoor:
data user runs Build _ Tracpool algorithm to generate probability Trapdoor T w The process is as follows:
1) representing the Chinese keyword w into a banded set;
2) generating the same random vector S' according to the strip set;
3) generating a signature vector T by using the same Q min hash functions;
4) randomizing the signature vector T to obtain a vector T';
5) calculating the Euclidean norm d (T, T');
6) generating a trapdoor Tw according to the vector T', the Euclidean norm d and the total number num of the required documents;
data owner will trap door T w And sending the encrypted data to a cloud server.
Step five, searching results:
after the cloud server receives the encrypted trapdoor, the trapdoor is obtained by decryption of a private key of the cloud server, and the obtaining steps are as follows:
1) cloud server decrypts trapdoor T with own public key w Obtaining Euclidean norm d, a vector T', and a required document total num;
2) the expansion vector T' is a set L;
3) converting each signature vector T stored in the fuzzy index table into a set L ', and calculating the Jaccard similarity JS between the set L and the set L'; provided JS ≠ 0, the two sets are similar, provided JS ≠ 0, calculating the euclidean norm d 'between the signature vectors T and T';
4) the error between the Euclidean norm d' and the Euclidean norm d of the keyword does not exceed a threshold value epsilon;
5) and acquiring corresponding documents according to the reverse index table, acquiring the relevance scores of the documents and the keywords in the reverse index table, and sending the documents to the data user in an ordered manner according to the rule that the relevance scores are from large to small.
Step six, obtaining a secret key:
the data user sends its attribute set Att to the trusted authority TAC, if the attribute set of the data user can pass the access control structure, the trusted authority sends the key to the data user; otherwise, returning to the position of T. The process is as follows:
the trusted authority receives the set Att of attributes, and if the attributes can access the control structure, the trusted authority selects a random number a E Z p And selecting a random number a for each attribute k ∈ Att k ∈Z p . Calculating a secret key
Introducing a recursive algorithm DecryptNode (CD, SK, x), and if the node x is a leaf node, enabling the node x to be a branch node
i Att (x), if i ∈ Att, then
If it is not
DecryptNode(CD，SK，x)＝⊥。
When x is not a leaf node, assuming z is all the child nodes of x, DecryptNode (CD, SK, z) is computed, and the output is stored as F z Let S stand out x Is of arbitrary size K x Is such that F z And ≠ T. If no such set exists, then the function returns ≠ T. Otherwise, calculating
Let a be DecryptNode (CD, SK, x).
Trusted authority TAC sends ciphertext document set
To the data user.
And step seven, the data user decrypts the returned ciphertext document set to obtain the required plaintext document. The method comprises the following specific steps:
for dataThe user uses his own private key for decryption
Obtaining a plaintext document (A, C, R); decryption by:
CT/(e(CR)/A)＝CT/(e(h s ，g (α+a)/β )/e(g，g) as )＝D。
in addition, it should be noted that the specific embodiments described in the present specification may be different in the components, the shapes of the components, the names of the components, and the like, and the above description is only an illustration of the structure of the present invention. Equivalent or simple changes in the structure, characteristics and principles of the invention are included in the protection scope of the patent. Various modifications, additions and substitutions for the specific embodiments described may be made by those skilled in the art without departing from the scope of the invention as defined in the accompanying claims.
Claims (8)
1. A searchable encryption method facing to cloud environment and supporting fuzzy keyword sequencing is characterized in that: the method comprises the following steps:
firstly, establishing and initializing a system, and generating a public parameter PP, a master key MK and a key K;
step two, generating an index: the data owner extracts the keyword set W according to the plaintext document set D, generates a reverse index table and a fuzzy index table, and sends the reverse index table and the fuzzy index table to the cloud server;
the steps of generating the reverse index table are as follows:
(1) if n documents and m keywords exist, setting the order of the reverse index table as (n +1) × (m + 1);
(2) setting the element of the first column (i +1, 1) coordinate of the reverse index table as an encrypted document number Enc K (id(D i ))，1≤i≤n；
(3) Setting the element of the first line (1, j +1) coordinate of the reverse index table as an encryption English keyword Enc K (W j )，1≤j≤m；
(4) Document D for elements of (i +1, j +1) coordinates of the rest elements in the inverted index table i And a keyword W j Correlation score of RF (W) j ，D i ) Filling;
(5) multiplying RF (W) by a random number r j ，D i )；
(6) Generating a reverse index table;
the step of generating the fuzzy index table is as follows:
(1) setting a fuzzy index table to be of (Q +1) × (m +1) order;
(2) chinese keywords w according to the Shingle method j Shingle is vector S' j ；
(3) Performing Q times of minimum hash calculation on the vector S by using Q MinHash functions to obtain Q real numbers, and forming a signature vector by using the Q real numbers;
(4) setting the first row (1, j) of the fuzzy index table as an encrypted English keyword Enc K (W j )，1≤j≤m；
(5) Setting the element f of the rest (i +1, j) coordinates of the fuzzy index table qi ：S′ j →R，1≤i≤Q；
(6) Generating a fuzzy index table;
step three, an encryption stage: the data owner encrypts the plaintext document set D by using the master key to generate a ciphertext document set CT, and sends the ciphertext document set CT to the cloud server;
step four, a trapdoor generation stage: constructing a trapdoor by a data user, encrypting the trapdoor and sending the trapdoor to a cloud server;
step five, a retrieval stage: after the cloud server receives the encrypted trapdoors, the trapdoors are obtained through decryption by using a private key of the cloud server, and the required documents are ordered according to the relevancy and sent to the data user;
step six, key obtaining stage: the data user sends the attribute set of the data user to the trusted authority, and if the attribute set of the data user can pass through the access control structure, the trusted authority sends the decryption key to the data user;
step seven, a decryption stage: and the data user decrypts the returned ciphertext document set to obtain the required plaintext document.
2. The cloud environment-oriented searchable encryption method supporting fuzzy keyword ranking according to claim 1, wherein: in the first step, the public parameter generating step is as follows:
(1) the data owner runs the setup function and selects a bilinear group G with the order of prime number p and generator G 0 Then from the minimal non-negative complete residual coefficient set Z of the prime number p p Selects three random numbers alpha, beta and r, and then issues common parameters
PP＝G 0 ，g，h＝g β ，e(g，g) α ；
(2) Setting the Master Key MK to (. beta., g) α ) Then a security parameter lambda is selected to generate a key
K＝(0，1) λ ；
(3) The data owner specifies the access control structure tau.
3. The cloud environment-oriented searchable encryption method supporting fuzzy keyword ranking according to claim 2, wherein: the access control structure tau is a tree, and each leaf node in the tau is composed of an attribute and a threshold k x 1 is formed; a non-leaf node is a threshold gate consisting of its child nodes and a threshold; set num x Is the total number of child nodes, k, of node x in the tree x Is the threshold value, and k is set to 0. ltoreq. k x ≤num x If k is x 1, the threshold gate is an OR gate, if k x ＝num x AND the threshold gate is an AND gate.
4. The cloud environment-oriented searchable encryption method supporting fuzzy keyword ranking according to claim 2, wherein: the document encryption step comprises:
for each node x, including leaf nodes, in the access control structure tau, a polynomial q is selected x (ii) a Traversing the whole access tree from top to bottom starting from the root node R of the access control structure tau, and enabling the polynomial q x Degree d of x BijieThreshold k for point x x Small 1, i.e. d x ＝k x -1；
Starting from the root node R, the algorithm selects a random number s ∈ Z p Let q stand for R (0) S, then randomly select d R Defining other points; for any other node x, let q x (0)＝q parent(x) (index (x)), and selecting the other d x Points are defined; let Y be the leaf node of τ, the document will encrypt according to the access tree line, compute the ciphertext CD:
wherein, the ciphertext CT ═ C 1 ，C 2 ，...，C n ，C i ＝D i e(g，g) αs ，1≤i≤n。
5. The cloud environment-oriented searchable encryption method supporting fuzzy keyword ranking according to claim 1, wherein: the trapdoor is constructed as follows:
1) representing the Chinese keyword w into a banded set;
2) generating the same random vector S' according to the strip set;
3) generating a signature vector T by using the same Q MinHash functions;
4) randomizing the signature vector T to obtain a vector T';
5) calculating the Euclidean norm d (T, T');
6) generating a trapdoor T according to the vector T', the Euclidean norm d and the total number num of the required documents w 。
6. The cloud environment-oriented searchable encryption method supporting fuzzy keyword ranking according to claim 5, wherein: the trapdoor is obtained by the following steps:
1) cloud server decrypts trapdoor T with own public key w Obtaining Euclidean norm d, a vector T', and a required document total num;
2) the expansion vector T' is a set L;
3) converting each signature vector T stored in the fuzzy index table into a set L ', and calculating the Jaccard similarity JS between the set L and the set L'; provided JS ≠ 0, the two sets are similar, provided JS ≠ 0, calculating the euclidean norm d 'between the signature vectors T and T';
4) the error between the Euclidean norm d' and the Euclidean norm d of the keyword does not exceed a threshold value epsilon;
5) and acquiring corresponding documents according to the reverse index table, acquiring the relevance scores of the documents and the keywords in the reverse index table, and sending the documents to the data user in an ordered manner according to the rule that the relevance scores are from large to small.
7. The cloud environment-oriented searchable encryption method supporting fuzzy keyword ranking according to claim 1, wherein: the concrete process of the step six is as follows: the trusted authority receives the attribute set Att, and if the attribute can be accessed to the control structure, the trusted authority selects a random number a E Z p And selecting a random number a for each attribute k ∈ Att k ∈Z p (ii) a Calculating a secret key
Introducing a recursive algorithm DecryptNode (CD, SK, x), if the node x is a leaf node, making
i Att (x), if i ∈ Att, then
If it is not
When x is not a leaf node, assuming z is all the child nodes of x, DecryptNode (CD, SK, z) is computed, and the output is stored as F z Let S stand out x Is of any sizeIs K x Is such that F z Not is equal to T; if no such set exists, the function returns ×; otherwise, calculating
Let a be DecryptNode (CD, SK, x);
trusted authority TAC sending
To the data user.
8. The cloud environment-oriented searchable encryption method supporting fuzzy keyword ranking according to claim 1, wherein: in step seven, decryption is performed by the following formula:
CT/(e(C，R)/A)＝CT/(e(h s ，g (α+a)/β )/e(g，g) as )＝D。
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